Scientists extract yeast from 5,300-year-old Iceman Otzi to bake bread

Yeast has been growing in the guts of Otzi the Iceman, a 5,300-year-old frozen mummy, scientists have discovered, and they used it to bake a sourdough bread. Otzi was strolling through the Alps on the border of Austria and Italy more than 5,300 years ago, before the Egyptian pyramids were built. Two German hikers stumbled across his mummified remains in 1991 in the northern Italian region of South Tyrol, and his well-preserved body has since been kept at minus six degrees Celsius, the same temperature as his icy tomb.

For the latest research, published in the Microbiome journal on Wednesday (June 3), an Italy-based team found evidence that both ancient and modern microbial life remain active in the frozen body.

"What we didn't expect to find was yeast," lead study author Mohamed Sarhan of the Eurac Research Institute in Bolzano told news agency AFP.

The scientists discovered four different cold-surviving yeasts in Oetzi's guts, skin and meltwater. Genetic analysis revealed DNA damage levels comparable to the original microbes in his guts, suggesting the yeast entered his body soon after death. "These yeasts have accompanied Oetzi on his long journey through the millennia," co-author Frank Maixner said.

The scientists then reproduced the gut yeast in a fridge. "If you tell anyone you have yeast, they immediately ask, 'Can we use it for bread?" Sarhan said. After three months of effort, "we had a very, very good sourdough", he said with a laugh. When asked about brewing beer, he responded: "It's on the list."

The study also flagged practical applications. When the mummy was found in 1991, phenol was used to prevent fungal growth, but the yeast was able to consume the chemical, suggesting future use in breaking down phenol in contaminated environments.

Beyond yeast, analysis of Oetzi's microbiome revealed gut bacteria nearly absent in modern industrialised humans but still found among tribes in Africa and South America and in 3,000-year-old faeces from a salt mine in Hallstatt, Austria.

The study concluded the Iceman is “not a biologically 'frozen' time-capsule but rather a complex ecosystem.” However, Nikolay Oskolkov of the Latvian Institute of Organic Synthesis cautioned that yeast samples were only taken in 2010 and 2019, providing "very little evidence that the yeasts have been multiplying over millennia," suggesting they were "relatively recent colonists of the mummy's body."